Conformationally Regulated CRISPR/Cas12a Activation Enabled by a Programmable DNA Dumbbell for Electrochemical SNP Genotyping

Single-nucleotide polymorphism (SNP) genotyping is crucial for genetic research and precision medicine, yet reliable discrimination of single-base variants in complex genomic backgrounds remains analytically challenging. Although CRISPR/Cas12a-based biosensing offers high sequence specificity, its intrinsic mismatch tolerance often leads to nonspecific activation by wild-type sequences, thereby compromising SNP fidelity. Herein, we report a highly sensitive electrochemical sensing platform based on a programmable DNA dumbbell (Dum) probe that functions as a conformational energy-barrier regulator of CRISPR/Cas12a activation. The closed-loop dumbbell architecture sterically shields the crRNA-activating sequence, establishing a high activation threshold that suppresses nonspecific Cas12a triggering. Only precise SNP hybridization induces a thermodynamically favorable conformational rearrangement, releasing the mediator and transitioning the CRISPR system from an inactive to an active state. To further enhance analytical sensitivity and reliability, nucleic acid–functionalized FeCo nanozymes were incorporated as catalytic signal transducers, enabling a self-validating dual-mode signal electrochemical readout through intrinsic metal redox and H 2 O 2 electrocatalysis. The resulting platform achieved reliably discriminates mutation abundances down to 0.1%. Validation using soybean genomic DNA samples demonstrates the robustness and practical applicability of the proposed strategy. This work establishes a conformational energy-barrier–regulated CRISPR activation paradigm, providing a generalizable analytical framework for high-fidelity SNP genotyping in molecular breeding and clinical diagnostics.